Hello,

I have recently installed a GM Hot Cam and Ls6 intake to my LS1. After the dyno tuning the transmission needed a rebuild.

After getting my car back with repaired transmission I have observed some terrible things.

Sometimes when I want to launch fast from stop (like a drag race) the transmission shifts from 1 to 3 causing the car to accelerate slow after 1st gear.
Also when I try to floor it, the transmission does not react and happily continues to ride on 3rd gear.

Also sometimes it does not react to kickdown during cruising.
All this happens on Drive as well as Overdrive modes.

What causes it? Will it go away once I change the oil after 1000 kilometers? Should I return the transmission, as it has warranty, to the guys who repaired it?

Also does the Hot Cam have influence on how the transmission shifts?
Sorry if some fo the questions sound rookie.

Thanks for any help.

Cheers
Marcin

 

Maf and tps calibration would be suspect, Quick shifts and no kickdown are not and cannot be a trans issue though they may result in one particulary the 3-4 clutch.

 

HERE IS MORE INFO AND NOTE THE CODE DOES NOT HAVE TO BE PRESENT FOR THIS CONDITION TO EXSIST .
PO121 CODE OR QUICK SHIFT 1-2-3-4 at WOT by 40 MPH FIX
Found this info on another forum and I know many people have popped up with this issue and wanted a fix. This would appear to be it. Hope it helps someone.

The curse of the P0121 Code... This code is infamous for giving people with larger cams fits...everything from traction control troubles, to shift point issues to just the good ole' P0121 code showing up for seemingly no reason making people scramble to purchase new Throttle Position sensors, adjust their set screws, etc, etc.

Before I go any further have a gander at the DTC information provided by LS2.com

http://www.ls2.com/boggs/dtcs/DTC%20P0121.htm

To outline a few key points

Quote:
The MAP is greater than 65 kPa

Quote:
The predicted throttle angle does not match the actual throttle angle

Quote:
All conditions present for 20 seconds

Now, that 65kpa map figure comes into play in nearly every LS1 Car/Truck because its the max map setting in most of the calibrations for the sanity test as shown here


Under normal circumbstances a stock cammed A4 will probably idle at around 35-40 map. When switching to a larger cam with more overlap your map readings could go up to as high as 70 or more kpa map which is way outside of the normal boundries. On a stock cammed car you'd probably need to be at around 30% tps to hit that same map number which is where that predicted throttle angle quote comes into play.

Now onto the last quote the 20 second timeframe. This will Usually come into play more often than not at idle with large cammed vehicles because many times your steady state map will be within the map sanity guidelines so there is a good possibity you might not see this code pop up immediatly.

There are a few ways you can cure this issue
a. Do as suggested in the help file which is to just set the min to 0 & max to 100
b. Adjust them to YOUR liking so you'll be within a reasonable limit. This will help determine if there IS a real issue with your TPS sensor later down the line.

So there you have it, as good an explanation I can come up with for that bastard code. So the next time you go WOT in your auto LS1 with a large cam & you go from 1st to 4th by 40mph or just a nagging p0121 code for no obvious reason you now have the info needed to fend it off.

 

mine did the same thing when the TPS sensor went bad. scan for codes and go from there

 

Aha, so it is not the transmission being badly rebuilt, but the tuning issue with the hot cam.

Thank you guys for that valuable help. I will contact my tuner and I will let him know. We also had problems tuning that Hot Cam on idle, it is still not smooth and sometimes when I shift from park to D, OD or R the car can loose rpms and just shut off

 

sounds like you need a new tuner

 

Thank you guys! The quickshift from 1-3 and no kickdown was exactly what mr performabuilt said. I also had wires from crankshaft position sensor burned by exhaust, that didn`t help either! The hot cam still has some tuning issues on idle but the transmission is shifting properly now. Thanks again I love you guys! Now gotta go kill some Porsches yuppiiiiiiii